The renal transport of sodium, potassium, chloride, bicarbonate and water in certain pathologic states will be studied using micropuncture techniques. It is intended to correlate function with structure and approach renal physiology and pathology from a biophysical standpoint. By studying the electrochemical potentials and reabsorption rates of various ions in a variety of pathologic and physiologic conditions and applying theoretical considerations of membrane transport, information concerning the regulation of the normal reabsorptive mechanisms of the aberrations of pathologic states will be obtained. Correlations of such functional studies with microdissection and histologic examination of the kidneys will be done.